A vehicle lane assist subsystem can provide assistance to a vehicle operator, e.g., via a steering subsystem can implement lateral and/or longitudinal control to maintain a vehicle in a road lane. However, such control depends on having sufficient confidence in data provided by vehicle sensors, and in resultant estimations of curvatures of a roadway, and a lane thereof, on which a vehicle is travelling. Assisted lane-keeping cannot be provided with sensors typically found on a vehicle in sub-optimal sensing conditions.